Method and apparatus for transmitting and receiving control information in wireless communication system

ABSTRACT

Methods, a Base Station (BS), and a User Equipment (UE) in a wireless communication system for transmitting and receiving control information are provided. The method for transmitting control information by a BS in a wireless communication system includes receiving information related to a signal transmitted by a second BS that the second BS which is a neighboring BS of the first BS, determining whether a second UE using an identical resource to that used by a first UE included in a cell of the first BS exists within a cell of the second BS based on the received information, when the second UE exists, generating control information for controlling a signal transmitted to the second UE by the second BS based on the received information, and transmitting the generated control information to the first UE through a control channel.

PRIORITY

This application claims the benefit under 35 U.S.C. § 119(a) of a Koreanpatent application filed in the Korean Intellectual Property Office onJun. 4, 2012 and assigned Serial No. 10-2012-0060023, the entiredisclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus for wirelesscommunication system. More particularly, the present invention relatesto a method and an apparatus for transmitting and receiving controlinformation in a wireless communication system.

2. Description of the Related Art

All signals and information degrading performance of a receiver of aUser Equipment (UE), other than a signal which the UE desires toreceive, is referred to as interference. Interference may be caused byan allocation of the same frequency resource of a UE from a serving BaseStation (BS) as that allocated to another UE from a neighboring BS.

A cell radius is very small in a next generation wireless communicationsystem, compared to an existing cellular environment, and the celldistribution is irregular due to the operation of various cells, such asa femto cell. Inter-cell interference in such an environment is a majorreason performance of the UE is degraded according to a packet error.

Accordingly, in order to address a difficulty in using a point-to-pointcommunication scheme of the related art, various interferencerecognition communication (i.e., interference aware cancellation)schemes have been suggested. One example of the interference recognitioncommunication schemes includes a scheme in which a UE removes aninterference signal from a reception signal by using control informationfor decoding the interference signal (hereinafter, referred to as“interference control information”).

In order to use the interference recognition communication scheme, theUE is required to receive the interference control information on aneighboring BS from a serving BS. However, since the interference signaland a neighboring cell environment for the UE are dynamically changed ina mobile communication environment and a degree of the change becomessignificant when the UE moves or a neighboring environment is changed,there is a limitation in that the UE continuously monitors whether theinterference control information is received. Further, since informationon an IDentifier (ID) of an interference cell or ID of an interferencecell UE used for acquiring the interference control information isreceived over a long period, it may not be possible to acquire theinterference control information for use every time according to therelated art.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide a method and an apparatus for transmitting andreceiving control information in a wireless communication system.

Another aspect of the present invention is to provide a method and anapparatus for transmitting and receiving control information fordecoding an interference signal using a common area of a control channelarea in a wireless communication system.

Another aspect of the present invention is to provide a method and anapparatus for enabling a User Equipment (UE) located in each cell toreduce influence of an interference signal affecting a neighboring BaseStation (BS) in a wireless communication system.

Another aspect of the present invention is to provide a method and anapparatus for discriminating and using a decoding process of aninterference signal considering whether to re-transmit the interferencesignal.

Another aspect of the present invention is to provide a method and anapparatus for reducing an overhead according to transmission/receptionof interference control information.

In accordance with an aspect of the present invention, a method fortransmitting control information by a first BS in a wirelesscommunication system is provided. The method includes receivinginformation related to a signal transmitted by a second BS from thesecond BS that is a neighboring BS of the first BS, determining whethera second UE using an identical resource to that used by a first UEincluded in a cell of the first BS exists within a cell of the second BSbased on the received information, when the second UE exists, generatingcontrol information for controlling a signal transmitted to the secondUE by the second BS based on the received information, and transmittingthe generated control information to the first UE through a controlchannel.

In accordance with another aspect of the present invention, a BS in awireless communication system for transmitting control information isprovided. The BS includes a BS interface unit, a transmitter, and acontroller. The BS interface unit is for receiving information, relatedto a signal transmitted by a neighbor BS, from the neighbor BS. Thetransmitter is for transmitting control information to a first UserEquipment (UE) through a control channel. The controller is forcontrolling the BS interface unit and the transmitter, for determiningwhether a second UE using an identical resource to that used by thefirst UE included in a cell of the BS exists within a cell of theneighbor BS based on the received information, for, if the second UEexists, generating control information for controlling a signaltransmitted to the second UE by the neighbor BS based on the receivedinformation, and for controlling to transmit the generated controlinformation to the first UE through a control channel.

In accordance with yet another aspect of the present invention, a methodfor receiving control information by a first UE in a wirelesscommunication system is provided. The method includes receiving controlinformation from a first BS through a control channel, receiving adesired signal from the first BS and an interference signal from asecond BS, the interference signal corresponding to use by a second UEwithin a cell of the second BS of a resource that is identical to aresource used by the first UE, decoding the control information toacquire interference information for controlling of the interferencesignal, and, when the interference information for one of decoding anddetecting the interference signal is acquired, decoding the desiredsignal and using the acquired interference information to mitigate theinterference signal.

In accordance with still another aspect of the present invention, a UEin a wireless communication system for receiving control information isprovided. The UE includes a receiver and a controller. The receiver isfor receiving control information from a first BS through a controlchannel, for receiving a desired signal from the first BS, and forreceiving an interference signal from a second BS, the interferencesignal corresponding to use by a another UE within a cell of the secondBS of a resource that is identical to a resource used by the UE. Thecontroller is for controlling the receiver, for decoding the controlinformation to acquire interference information for controlling of theinterference signal, and for, when the interference information for oneof decoding and detecting the interference signal is acquired, decodingthe desired signal and using the acquired interference information tomitigate the interference signal.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram illustrating a wireless communication systemaccording to the related art.

FIG. 2 is a flowchart illustrating a process of decoding a signalreceived from a Base Station (BS) by a User Equipment (UE) in a wirelesscommunication system according to the related art.

FIG. 3 is a diagram illustrating a wireless communication systemaccording to an exemplary embodiment of the present invention.

FIG. 4 is a flowchart illustrating a process of transmittingProprietary-Downlink Control Information (P-DCI) by a serving BSaccording to an exemplary embodiment of the present invention.

FIG. 5 is a flowchart illustrating a process of receiving P-DCI by a UEaccording to an exemplary embodiment of the present invention.

FIG. 6 is a block diagram illustrating a serving BS according to anexemplary embodiment of the present invention.

FIG. 7 is a block diagram illustrating a UE according to an exemplaryembodiment of the present invention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Exemplary embodiments of the present invention provide a method and anapparatus for transmitting/receiving interference control information ina wireless communication system. More particularly, exemplaryembodiments of the present invention provide a method and an apparatusin which a User Equipment (UE) located in each cell detects aninterference signal for a neighboring Base Station (BS) and removes theinterference signal from a reception signal in a wireless communicationsystem including a plurality of BSs.

In an exemplary embodiment of the present invention, a serving BStransmits information on a transmission scheme used for determining acharacteristic of a transmission signal of a neighboring BS to a UE of aserving cell as control information for decoding an interference signal(hereinafter, referred to as “interference control information”).Further, in the exemplary embodiments of the present invention, atechnique for using the interference control information based on amobile communication standard, and a method and an apparatus forefficiently reducing interference by discriminating initial transmissionand re-transmission in a wireless communication system using, forexample, a Hybrid Automatic Retransmit Request (HARQ) scheme aresuggested.

In the meantime, an example of the wireless communication systemaccording to the exemplary embodiments of the present invention includesa wireless communication system, such as Global System for Mobilecommunications (GSM), a Wideband Code Division Multiple Access (WCDMA)system, Universal Mobile Telecommunications System (UMTS), and a LongTerm Evolution (LTE) system, requiring an interference control.

Hereinafter, prior to explaining the exemplary embodiments of thepresent invention, a wireless communication system will be described.

FIG. 1 is a diagram illustrating a wireless communication systemaccording to the related art.

Referring to FIG. 1, the wireless communication system includes a firstBS 100, a first UE 110 for receiving a signal from the first BS 100, asecond BS 120 which is a neighboring BS of the first BS 100, and asecond UE (not shown) for receiving a signal from the second BS 120.

Since the first BS 100 is a serving BS of the first UE 110, the secondBS 120 may be an interference BS generating interference to the first UE110. That is, when the second BS 120 transmits a signal to the second UEby using the same resource as a resource used by the first UE 110, thesignal transmitted from the second BS 120 may be received in the firstUE 110 as the interference signal according to a location of the firstUE 110 and transmission power of the second BS 120. As such, since thefirst UE 110 may receive an unintended interference signal, a receptionperformance of the first UE 110 is determined based on a strength of theinterference signal. This will be described in detail below.

Equations 1 and 2 simply represent a reception signal of the first UE110.y=√{square root over (p _(D))}h ^(D) x ^(D) +n  (1)y=√{square root over (p _(D))}h ^(D) x ^(D)+√{square root over (P_(I))}h ^(I) x ^(I) +n  (2)

Equation (1) represents a desired signal which the first UE 110 receivesand equation (2) represents the desired signal and the interferencesignal which the first UE 110 receives. For example, equation (1)represents the signal which the first UE 110 receives from the first BS100 that is the serving BS, and equation (2) represents the signalswhich the first UE 110 receive from the first BS 100 and the second BS120 that is the interference BS.

In equations (1) and (2), y indicates a signal which the first UE 110receives for each antenna, x indicates a signal transmitted from acorresponding BS, and h indicates a channel value of a wirelesscommunication environment for each signal. Further, n indicates a noisesignal generated in the antenna of the first UE 110 and p indicates atransmission power value of each transmitted signal. Furthermore, D andI in each signal indicate a desired signal and an interference signal,respectively.

In equations (1) and (2), a plurality of signals may be indicatedaccording to the number of antennas, but in the following description,it is assumed that a signal is received using one antenna.

An operation of a receiver of a UE of the related art includes anoperation of estimating a channel value h by using a reception signal yand a specific reference signal, decoding a signal based on theestimated channel value, and determining whether a reception of a signalis successful. In order to perform such an operation, the accurateestimation of the channel value is important. For the accurateestimation of the channel value, a signal, i.e., a Reference Signal(RS), having a predetermined pattern between the BS and the UE, is used.

A value of a transmission signal x corresponding to a position of the RSmay be re-generated based on information received from the BS by the UE.In this case, when only a noise is received in the signal of equation(1), a channel estimation performance is determined according to aSignal to Noise Ratio (SNR). In general, when the SNR is high, thechannel may be accurately estimated, thereby increasing a decodingsuccess possibility of the UE.

However, in the environment of equation (2), i.e., an environmentincluding the interference signal, even when the SNR is high, theinterference signals x^(I) and h^(I) affect the channel estimationperformance. Especially, when the interference signal exists and thechannel estimation for the interference signal is not accurate, theinterference signal itself affects the desired signal, resulting in thedeterioration of the performance of the UE.

In order to address the aforementioned problem, an InterferenceWhitening (IW) method, a symbol level joint detection method, a bitlevel detection method, etc. are used in the related art.

The IW method is a method of improving performance of the receiver byignoring the interference signal received from the interference BS orassuming that the interference signal is a noise. The IW method will nowbe described with reference to equations (3) to (6).

The received signal of equation (2) may be indicated as equation (3).y=√{square root over (p _(D))}h ^(D) x ^(D) +v(v=√{square root over (P_(I))}h ^(I) x ^(I) +n)  (3)

In equation (3), v indicates an addition of the remaining signals,except for the desired signal to be received. A covariance for thesignal v is represented as equation (4).R _(v) =P _(I) h ^(I+)+σ_(n) ² I  (4)

In equation (4), R_(v) indicates a covariance value for the signal v,σ_(n) ² indicates a noise variance, and I indicates an identity matrix.

The calculated covariance value may be represented as equation (5) byusing various decomposition schemes, e.g., a Cholesky decompositionscheme.R _(v) =P _(v) ^(−1/2) R _(v) ^(1/2)  (5)

An IW method of the related art is performed by applying a decompositionresult value obtained by using equation (5) to the reception signal y.Through the aforementioned method, a result, such as equation (6), isgenerated. In equation (6), {tilde over (y)} indicates a result signalaccording to the IW, so that the decoding process may be performed byusing a receiver which does not consider the interference.{tilde over (y)}=P _(v) ^(−1/2) y=√{square root over (P _(D))}R _(v)^(−1/2) h ^(D) x ^(D) +{tilde over (v)}  (6)

The IW method is a method of improving a reception performance byconverting the interference signal to a noise when it is determined thatit is possible to apply a whitening scheme to the interference signal.Accordingly, when it is desired to use the IW method, the constructionfor accurately determining a strength of the interference signal isadditionally implemented and it is determined whether to apply thewhitening scheme to the interference signal. Further, since theperformance of the IW method is greatly varied according to a rank ofthe interference signal and the number of reception antennas, there is aproblem of failing to regularly maintain the performance according tothe wireless communication environment.

Next, the symbol level joint detection method will be described.

The symbol level joint detection method is a method of improving theperformance of the receiver by detecting modulation information on theinterference signal received from the interference BS and then joiningthe modulation information and interference information by a UE of theserving BS (hereinafter, referred to as a “serving cell UE”). That is,the symbol level joint detection method is a method of detecting anormal signal to be received from the serving BS considering atransmission scheme (e.g., a modulation order) of the interferencesignal received by the serving cell UE. For the performance of themethod, the serving cell UE detects the modulation information on theinterference signal or receives information on interference from theserving BS.

The symbol level joint detection method provides excellent performancecompared to the IW method, but a difference of the performance is verylarge according to the indirect detection of the interference signalfrom the reception signal without receiving the interference informationfrom the serving BS. Further, the symbol level joint detection methodhas a shortcoming in that there is a noticeable degradation of thedetection performance for a higher modulation order, such as 64Quadrature Amplitude Modulation (64QAM), compared to the detectionperformance for a lower modulation order, such as Quadrature Phase ShiftKeying (QPSK) and 16QAM.

Next, the bit level detection method will be described.

The bit level detection method is a method, in which a serving BStransmits interference control information received from an interferenceBS to a serving cell UE for the serving cell UE and the serving cell UEdecodes and uses an interference signal of the interference cell UEbased on the interference control information, thereby more accuratelyremoving the interference signal.

The bit level detection method has a high complexity, but shows anexcellent performance compared to the symbol level joint detectionmethod. That is, the bit level detection method may maximize theperformance of the UE in an aspect that the method may use everyavailable signal. However, since the UE continuously monitors theinterference control information, substantial power is consumed and theinterference control information has a structure that is susceptible toerror (e.g., a false alarm).

Further, in a wireless communication system, such as an LTE system,using a protocol by which control information, e.g., information on atransmission mode and an IDentifier (ID) of a UE, transmitted over along period between a BS and a UE and control information, e.g., HARQ,Modulation and Coding Scheme (MCS), and resource information,transmitted in the unit of a frame are discriminated from each other andtransmitted, when the UE fails to receive the control informationtransmitted over a long period, there is a problem in that the UE maynot accurately acquire the control information on the interferencesignal even if the UE has properly received the control informationtransmitted in the unit of a frame. Further, when the controlinformation on the interference signal is not accurately decoded, theefficiency of the interference recognition communication isdeteriorated.

In the meantime, in order to use the symbol level joint detection methodand the bit level detection method, the serving cell UE searches for theminimum information capable of inducing information on signalstransmitted by the interference BS by itself. Or, the serving cell UEreceives information on a plurality of transmission signals of theinterference BS, which may generate the interference to the serving cellUE, from the serving BS. To this end, the serving BS may receive theinterference control information from the interference BS through abackhaul channel 140, etc. illustrated in FIG. 1 and transmit thereceived interference control information to the serving cell UE.

In the meantime, in order for the serving cell UE to receive theinterference control information, a process of processing information bythe UE illustrated in FIG. 2 is performed.

FIG. 2 is a flowchart illustrating a process of decoding a signalreceived from a BS by a UE in the wireless communication systemaccording to the related art.

FIG. 2 illustrates an example of a case where the wireless communicationsystem is an LTE system. However, the example is equally applicable toother wireless communication systems. FIG. 2 is a flowchart illustratinga process according to a general flow, and does not necessarily reflecta temporal flow.

Referring to FIG. 2, the UE detects a cell ID of a cell to which the UEcurrently belongs through a cell search operation in step 200. Next, theUE receives and decodes system information, i.e., a Master SystemInformation (MIB) block, broadcasted from the BS based on the detectedcell ID in step 202. The MIB may include one or more of a systembandwidth, a frame number, transmitter antenna configurationinformation, etc., and may be transmitted through a Primary Broadcastcontrol CHannel (PBCH).

In step 204, the UE decodes a Control channel Format Indicator (CFI)transmitted through a Physical Control Format Indicator CHannel (PCFICH)based on the information acquired in steps 200 and 202. The CFI, whichis UE specific information, indicates an area of a resourcecorresponding to a control channel. The UE determines that it ispossible to use the remaining areas, other than the area indicated bythe CFI, as data areas.

In step 206, the UE decodes control information on system informationfor the UE based on the information acquired in steps 200 through 204.The control information is transmitted through a Physical DownlinkControl CHannel (PDCCH). A PDCCH area for transmitting the controlinformation includes a Common Search Space (CSS), in which the controlinformation may be decoded without using the specific information on theUE.

In step 208, the UE decodes the system information for the UE based onthe information acquired in steps 200 through 206. The systeminformation includes an ID of the UE and information controlled over along period, such as a transmission mode including a Multiple InputMultiple Output (MIMO) mode. Further, the system information istransmitted through a Physical Downlink Shared CHannel (PDSCH) and maybe transmitted in various patterns and various cycles according to atype of corresponding information.

In step 210, the UE decodes control information on traffic datatransmitted to the UE based on the information acquired in steps 200through 208. The control information is transmitted through the PDCCH.The control information includes one or more of a modulation order, aresource allocation, a pre-coding matrix, a HARQ process number, a newdata indicator, a redundancy version, a HARQ swap flag, etc. A PDCCHarea for transmitting the control information on the traffic data isreferred to as a UE specific Search Space (USS), and the controlinformation may be decoded in the USS only when information on adecoding start position is acquired by using information on the ID ofthe UE.

In step 212, the UE decodes the traffic data transmitted to the UE basedon the information acquired in steps 200 through 208. The traffic datais transmitted through the PDSCH.

The UE performs the process of FIG. 2 in order to demodulate the signalof the serving BS. In this case, one of the most important items ofinformation for the demodulation is an information block size. A schemeof transmitting the information block size in the LTE system is relatedto the HARQ operation. The HARQ operation includes an operation, inwhich, when the decoding of a reception signal fails, a UEsimultaneously stores the reception signal and transmits a signalindicating the failure of the decoding of the reception signal to aserving BS, thereby enabling the serving BS to determine whether tore-transmit the corresponding signal. In general, the LTE systemsupports the HARQ operation for the data transmission.

In the HARQ used in most wireless communication systems, when the UEfails to decode the reception signal, the serving BS transmits anothersignal generated based on the same information as that on the initialtransmission in retransmitting the signal, so that the UE may obtain again by re-combining the retransmitted signal with the initiallytransmitted signal.

However, contrary to HARQ of the related art, a process of acquiring aninformation block size for the decoding is changed according to a stepof performing the HARQ operation in the HARQ used in the LTE system.That is, in the LTE system, the UE detects and decodes the informationblock size (i.e., transport block size) from the initially transmittedcontrol information, and stores the corresponding information block sizewhen the UE fails to decode. Then, when the same signal as thecorresponding signal is retransmitted, the UE is not able to extract theinformation block size from control information on the retransmittedsignal, so that the UE stores the information block size stored in theinitial transmission of the same HARQ packet.

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail.

The exemplary embodiments of the present invention provide a method andan apparatus for reducing interference from a neighboring BS by a UEbelonging to each cell in a wireless communication system including aplurality of BSs. More particularly, the exemplary embodiments of thepresent invention provide a method and an apparatus for transmittingtransmission scheme information through which a characteristic of asignal transmitted from an interference BS may be recognized as newcontrol information (i.e., interference control information) to aserving cell UE by a serving BS.

In the following exemplary embodiments of the present invention, theinterference control information transmitted to the serving cell UE isdefined as Proprietary-Downlink Control Information (P-DCI). The P-DCIincludes information on a transmission scheme of the interference BS forthe interference cell UE and information on an operation of a BSnetwork. Contents on the information contained in the P-DCI will bedescribed in detail further below.

The exemplary embodiments of the present invention suggest a techniquefor using the P-DCI based on a mobile communication standard and providea method and an apparatus for efficiently reducing influence ofinterference by discriminating an initial transmission and aretransmission in the wireless communication system using the HARQretransmission scheme as one example.

First, an example of the wireless communication system according to anexemplary embodiment of the present invention will be described withreference to FIG. 3.

FIG. 3 is a diagram illustrating a wireless communication systemaccording to an exemplary embodiment of the present invention.

Referring to FIG. 3, the wireless communication system includes a firstBS 300, a first UE 310 receiving a signal from the first BS 300, asecond BS 320 which is a neighboring BS of the first BS 300, and asecond UE (not shown) receiving a signal from the second BS 320.

The first BS 300 and the second BS 320 represent transmitters used in awireless communication system. For example, when the wirelesscommunication system is the LTE system, each of the first BS 300 and thesecond BS 320 may be an evolved Node B (eNodeB), and when the wirelesscommunication system is the UMTS (WCDMA) system, each of the first BS300 and the second BS 320 may be a Node B (NodeB). Further, when thewireless communication system uses a signaling for conforming to acommunication standard, each of the first BS 300 and the second BS 320may be a BS having a broad meaning including an Evolved Packet Core(EPC) or a Radio Network Controller (RNC).

Further, the backhaul channel 330 is a simplification of various networkconstructions for connecting the respective BSs in a wirelesscommunication network, and indicates a transmission channel forsignaling and exchanging data between different BSs in the exemplaryembodiment of the present invention. The first BS 300 and the second BS320 may share information through the backhaul channel 330.

More particularly, the first BS 300 and the second BS 320 shareinformation on a plurality of UEs of which the performance may bedegraded due to the inter cell interference. The first BS 300 determinesinformation on the interference cell UE sharing the same resource (alsoreferred to as the resource that is “co-scheduled” between the BSs) witha specific UE desiring to currently transmit a signal based on theinformation received from the second BS 320 (and possibly one or moreBSs in addition to the second BS 320) which is the neighboring BS withina specific cell.

The first BS 300 generates interference control information, i.e., theP-DCI, for the first UE 310 by using the information on the interferencecell UE and transmits the generated P-DCI to the first UE 310. Also, thefirst BS 300 may transmit the generated P-DCI to the second BS 320through the backhaul channel 330.

The first BS 300 transmits the P-DCI using a CSS area within the PDCCHarea of the serving cell. As described above, in the CSS area, thesignal may be demodulated without using the information on the ID of theUE. The first UE 310 may not determine whether the P-DCI exists beforethe reception of the P-DCI, and thus demodulates the P-DCI in a state ofnot being aware of the ID of the UE for the interference signal, so thatthe P-DCI is transmitted by using the CSS area.

However, when the first UE 310 has already acquired the ID of the UE forthe interference signal, the P-DCI may also be transmitted by using theUSS area. Further, the P-DCI is the interference information, but may betransmitted after being masked using the ID, e.g., a Cell-Radio NetworkTemporary Identifier (C-RNTI) or a UE-RNTI), of the serving cell UE.

Accordingly, the first UE 310 may achieve excellent performance by usingthe efficient detection and decoding scheme based on the P-DCI receivedfrom the first BS 300, compared to a case where no interferenceinformation is used.

In the meantime, FIG. 3 has been described based on an example of a casein which the first UE 310 receives the P-DCI from one BS, i.e., thefirst BS 300, but the first UE 310 may receive the P-DCI from one ormore other neighboring BSs, as well as the first BS 300, according toanother exemplary embodiment of the present invention. In this case, thefirst UE 310 may monitor whether the P-DCI is transmitted from any ofthe plurality of BSs.

In the meantime, a format of the P-DCI according to an exemplaryembodiment of the present invention may be represented as Table 1.

TABLE 1 Parameter Explanation Bits Transport block to Indicates whetherto swap a channel when codeword swap flag two transport blocks aretransmitted through a spatial multiplexing HARQ process HARQ processnumber of a transport number block transmitted in a correspondingsubframe Transport block 1 Modulation and coding scheme New dataindicator (To determine whether to retransmit HARQ information)Redundancy version (Information on a start position of a transmittedpacket within an encoded packet) Transport block 2 Modulation and codingscheme New data indicator Redundancy version Pre-coding informationPre-coding matrix index for an interference signal when the interferencesignal is transmitted using the pre-coding Cell ID Interference Cell IDUE ID Interference UE ID 6 Transmission mode Interference transmissionmode CFI Interference control formation indicator Total Total number ofbits of P-DCI 2

As illustrated in Table 1, the P-DCI includes the “Transport block tocodeword swap flag” indicating whether to swap the channel when twotransport blocks are transmitted through a spatial multiplexing in theinterference cell; the “HARQ process number” indicating a HARQ processnumber of a transport block transmitted in a corresponding subframe; the“Transport block 1” and the “Transport block 2” including information ona modulation scheme and a coding scheme, and information on a new dataindicator and information on a redundancy version, respectively; the“Pre-coding information” indicating a pre-coding matrix index for aninterference signal when the interference signal is transmitted usingthe pre-coding; the “Cell ID” indicating an ID of an interference cell;the “UE ID” indicating an ID of an interference cell UE; the“Transmission mode” indicating a transmission mode used in aninterference cell; the “CFI” indicating an interference controlinformation indicator; and the “Total” indicating the total number ofbits of the P-DCI.

The “Transport block 1’, the “Transport block 2”, “HARQ process number”,and “Transport block to codeword swap flag” among the information in theP-DCI represented in Table 1 are information which the first UE 310 usesfor the decoding of the interference information. Further, the “HARQprocess number”, and the “new data indicator” and the “redundancyversion” included in the “Transport block 1” and the “Transport block 2”among the information in the P-DCI are information used for the processof the HARQ retransmission.

For the performance of the decoding of the signal, information on a sizeof an information block is generally needed. In the LTE system, theinformation on the information block size may be acquired based on theinformation on the modulation scheme and the coding scheme, the resourceblock information, and the information indicating whether the HARQretransmission is performed. The information indicating whether the HARQretransmission is performed may be acquired based on whether theinformation of 1 bit included in the “new data indicator” of the“transport block 1” and the “transport block 2” is toggled (i.e., anoperation of changing “0” to “1” or changing “1” to “0”). That is, whenthe information of 1 bit included in the “new data indicator” istoggled, it is determined as the HARQ initial transmission, but when theinformation of 1 bit included in the “new data indicator” is nottoggled, it is determined as the HARQ retransmission.

When the information of 1 bit included in the “new data indicator” istoggled so that it is determined as the HARQ initial transmission, theUE determines a size of the information on the received interferencesignal, i.e., a transport block size, by using the information on the“modulation and coding scheme” among the information on the P-DCI andinformation on a Resource Block (RB) within a serving DCI of the UE.Further, the UE detects and decodes the interference signal based on thetransport block size and removes the interference signal from thereception signal.

When the information of 1 bit included in the “new data indicator” hasnot been toggled so that it is determined as the HARQ retransmission,the UE has difficulty in determining the transport block size, so thatthe UE detects the interference signal based on the information on the“modulation and coding scheme”. Further, the UE decodes the receptionsignal without decoding the interference signal.

In the meantime, the P-DCI may be transmitted over, for example, asubframe period, but the transmission period of the P-DCI is not limitedthereto and may be variously changed. The P-DCI may include the entiretyor a part of the information represented in Table 1 according to anexemplary embodiment of the present invention.

For example, the P-DCI may be configured in a form including onlyinformation on a transmission mode used in the interference cell asrepresented in Table 2. That is, when a load of the serving BS is large,the serving BS may transmit the P-DCI configured with parametersrepresented in Table 2 to the UE. In this case, the UE may acquirecorresponding information by directly receiving and decoding theremaining information (e.g., the remaining information included in Table1 excluding the information included in Table 2) for the detection orthe decoding of the interference signal.

TABLE 2 Parameter Explanation Bits Transmission mode Interferencetransmission mode 2 CFI Interference control information indicator 2Total Total number of bits of P-DCI 4

In the meantime, the P-DCI may be configured in another format includinginformation represented in Table 3.

TABLE 3 Parameter Explanation Bits Transport block to Indicates whetherto apply a swapped 1 codeword swap flag channel when two transportblocks are transmitted through a spatial multiplexing Transport block 1Modulation and coding scheme 5 Transport block 2 Modulation and codingscheme 5 Transmission mode Interference transmission mode 2 CFIInterference control information indicator 2 Total Total number of bitsof P-DCI 15

As represented in Table 3, the P-DCI may be configured in the formatincluding information, through which information on a modulation ordermay be acquired, among various interference information. It may not bepossible to use the information on the modulation order for the decodingof the interference signal. However, the information on the modulationorder may be used for the detection of the interference signal.Accordingly, even if the P-DCI configured with the informationrepresented in Table 3 is transmitted, the UE recognizes theinterference signal, thereby reducing the influence of the interferencesignal.

In the meantime, three formats of the P-DCI represented in Tables 1 to 3have been suggested in the exemplary embodiments of the presentinvention, but the format of the P-DCI is not limited thereto and mayinclude various combinations of the information represented in Table 1as a matter of course.

Hereinafter, a process of the operation of the serving BS according toan exemplary embodiment of the present invention will be described withreference to FIG. 4.

FIG. 4 is a flowchart illustrating a process of transmitting P-DCI by aserving BS according to an exemplary embodiment of the presentinvention.

Referring to FIG. 4, the serving BS exchanges scheduling informationwith a neighboring BS in step 400. That is, the serving BS transmits thescheduling information for UEs within a serving cell to the neighboringBS and receives scheduling information for UEs within a neighboring cellfrom the neighboring BS. The scheduling information may be periodicallyexchanged. Alternatively, the scheduling information may be exchangedbased on a triggering event.

The serving BS determines whether an interference cell UE using the sameresource as that used in at least one serving cell UE desiring tocurrently transmit a signal exists based on the received schedulinginformation in step 402.

When the serving BS determines that the interference cell UE exists instep 404, the serving BS generates P-DCI for the serving cell UE basedon the information on the interference cell UE in step 406. Theinformation on the interference cell UE may be acquired from thereceived scheduling information, and may include, for example, an ID ofthe interference cell, an ID of the interference cell UE, and atransmission mode of the interference cell, etc. When the generation ofthe P-DCI is completed, the serving BS transmits the generated P-DCI tothe serving cell UE in step 408.

In the meantime, when the serving BS determines that the interferencecell UE does not exist in step 404, the serving BS determines that thereis no interference signal and completes all processes.

Next, a process of an operation of a UE according to an exemplaryembodiment of the present invention will be described with reference toFIG. 5.

FIG. 5 is a flowchart illustrating a process of receiving P-DCI by theUE according to the exemplary embodiment of the present invention.

Referring to FIG. 5, the UE receives a signal from a serving BS anddecodes the signal for a CSS area in step 500. Further, when the P-DCIis transmitted through the CSS area in which the decoding is performed(i.e., in a case where the P-DCI is transmitted through the USS areawhen an ID of the UE is acquired), the UE decodes the P-DCI in step 502.

The UE determines whether the decoding of the P-DCI is successful instep 504. When the decoding of the P-DCI fails, the UE determines thatthere is no interference or that it is not able to identify interferenceinformation, and proceeds to step 516 of performing a decoding processof the related art without considering the interference.

However, when the decoding of the P-DCI is successful, the UE proceedsto step 506 to acquire the interference information from the decodedP-DCI. Next, the UE determines whether all interference information forthe decoding of the interference signal is acquired in step 508. Forexample, the UE determines whether all interference informationrepresented in Table 1 or the information on the modulation order forthe interference signal represented in Table 3 is acquired. Here, inmaking this determination, the UE may consider remaining informationthat it can receive and decode as part of the acquired interferenceinformation for the decoding of the interference signal. For example,when the interference information represented in Table 2 is acquired,the UE may determine this as scenario where all interference informationfor the decoding of the interference signal is acquired because the UEcan acquire the remaining information for the decoding of theinterference signal. In the case where the interference informationrepresented in Table 2 is acquired, the UE will receive and decode theremaining information for the decoding of the interference signal.

When the UE acquires all interference information for the decoding ofthe interference signal, the UE detects information for the decoding ofthe interference signal from the acquired interference information andcombines the detected information for the decoding of the interferencesignal with information for the decoding of a desired signal in step510. Next, the UE detects the interference signal and the desired signalfrom the received signal by using the combined decoding information instep 512. Further, the UE decodes the detected interference signal andthe detected desired signal and removes the decoded interference signalfrom the received signal in step 514.

In the meantime, when the UE does not acquire all interferenceinformation for the decoding of the interference signal, i.e., acquiresthe information on the modulation order for the interference signal, theUE detects the interference signal and the desired signal based on theinformation on the modulation order for the interference signal in step518. The information on the modulation order for the interference signalmay not be used for the decoding of the interference signal, but may beused for the detection of the interference signal. Next, the UE excludesthe detected interference signal from the received signal and decodesthe detected desired signal in step 520.

Hereinafter, a construction of the serving BS and the UE according toexemplary embodiments of the present invention will be described withreference to FIGS. 6 and 7.

FIG. 6 is a block diagram illustrating a serving BS according to anexemplary embodiment of the present invention.

Referring to FIG. 6, the serving BS includes a transmitter 600, areceiver 602, a BS interface unit 604, a memory 606, and a controller608.

The transmitter 600 and the receiver 602 are elements used forperforming communication with a serving cell UE. That is, thetransmitter 600 transmits a signal and data to the serving cell UE, andthe receiver 602 receives a signal and data from the serving cell UE.Although it is not illustrated in FIG. 6, the transmitter 600 mayinclude an encoder and a modulator for encoding and modulating atransmission signal.

The BS interface unit 604 performs communication with at least oneneighboring BS. More particularly, the BS interface unit 604 exchangesscheduling information with the neighboring BS. That is, the BSinterface unit 604 transmits the scheduling information for UEs within aserving cell to the neighboring BS and receives the schedulinginformation for UEs within a neighboring cell from the neighboring BS.The scheduling information may be periodically exchanged. Alternatively,the scheduling information may be exchanged based on a triggering event.

The memory 606 stores all information and data generated during theoperation of the serving BS. Especially, the memory 606 stores the P-DCIdescribed herein in the exemplary embodiments of the present invention.

The controller 608 determines the operation of the serving BS bycontrolling the transmitter 600, the receiver 602, the BS interface unit604, and the memory 606.

The controller 608 controls to exchange the scheduling information withthe neighboring BS, and determines whether an interference cell UEsharing the same resource with at least one serving cell desiring tocurrently transmit a signal exists based on the scheduling informationreceived from the neighboring BS.

When the controller 608 determines that the interference cell UE exists,the controller 608 generates P-DCI for the serving cell UE based on theinformation on the interference cell UE. The information on theinterference cell UE may be acquired from the received schedulinginformation, and may include, for example, an ID of the interferencecell, an ID of the interference cell UE, and a transmission mode of theinterference cell. When the controller 608 completes the generation ofthe P-DCI, the controller 608 controls to transmit the generated P-DCIto the serving cell UE by controlling the transmitter 600. Also, thecontroller 608 may transmit the generated P-DCI to the neighboring BSthrough a backhaul channel.

In the meantime, when the controller 608 determines that theinterference cell UE does not exist, the controller 608 determines thatthere is no interference signal and does not generate the P-DCI.

FIG. 7 is a block diagram illustrating a UE according to an exemplaryembodiment of the present invention.

Referring to FIG. 7, the UE includes a transmitter 700, a receiver 702,a memory 706, and a controller 708.

The transmitter 700 and the receiver 702 are elements for wirelesscommunication of the UE. The transmitter 700 transmits a signal and datato a serving BS, and the receiver 702 receives a signal and data fromthe serving BS and may receive a signal of a neighboring BS, as aninterference signal. Further, although it is not illustrated in FIG. 7,the receiver 702 may include a demodulator and a decoder fordemodulating and decoding a reception signal.

The memory 706 stores all information and data generated during theoperation of the UE. Especially, the memory 706 stores the P-DCIdescribed herein in the exemplary embodiments of the present invention.

The controller 708 determines the operation of the UE by controlling thetransmitter 700, the receiver 702, and the memory 706.

The controller 708 controls to receive a signal from the serving BS anddecodes the signal for the CSS area. Further, when the P-DCI istransmitted through the CSS area in which the decoding is performed, thecontroller 708 decodes the P-DCI.

The controller 708 determines whether the decoding of the P-DCI issuccessful. When the decoding of the P-DCI is fails, the controller 708determines that there is no interference or that it is not able toidentify interference information, and performs a related art decodingprocess without considering the interference.

However, when the decoding of the P-DCI is successful, the controller708 acquires the interference information from the decoded P-DCI. Next,the controller 708 determines whether all interference information forthe decoding of the interference signal is acquired. For example, thecontroller 708 determines whether all interference informationrepresented in Table 1 or the information on the modulation order forthe interference signal represented in Table 3 is acquired.

When the controller 708 acquires all interference information for thedecoding of the interference signal, the controller 708 detectsinformation for the decoding of the interference signal from theacquired interference information and combines the detected informationfor the decoding of the interference signal with information for thedecoding of a desired signal. Next, the controller 708 detects theinterference signal and the desired signal from the received signal byusing the combined decoding information. Further, the controller 708decodes the detected interference signal and the detected desired signaland removes the decoded interference signal from the received signal.

In the meantime, when the controller 708 does not acquire allinterference information for the decoding of the interference signal,i.e., acquires the information on the modulation order for theinterference signal, the controller 708 detects the interference signaland the desired signal based on the information on the modulation orderfor the interference signal. The information on the modulation order forthe interference signal may not be used for the decoding of theinterference signal, but may be used for the detection of theinterference signal. Next, the controller 708 excludes the detectedinterference signal from the received signal and decodes the detecteddesired signal.

Accordingly, it is not necessary for the exemplary embodiments of thepresent invention to demodulate the interference control information(e.g., the DCI information) generally used for acquiring the controlinformation for the interference signal or store correspondinginterference information.

Further, when the interference control information (i.e., P-DCI)transmitted in the unit of a frame as described herein in the exemplaryembodiments of the present invention is used, it is not necessary tomonitor and store information on the ID of the UE and the transmissionmode allocated over a long period for the decoding of the interferencesignal.

Further, since the information on the interference signal according tothe co-scheduling is transmitted in the exemplary embodiments of thepresent invention, it is not necessary to transmit information on anallocation type and resource allocation.

Further, the exemplary embodiments of the present invention insert onlyinformation used for maximizing the performance to the interferencecontrol information, thereby reducing an overhead for the interferencecontrol information. Especially, since the exemplary embodiments of thepresent invention uses the common resource for the co-scheduling, it ispossible to acquire the additional information on the interferencesignal by using both the DCI information and the interference controlinformation of the UE. Further, the exemplary embodiments of the presentinvention may acquire the information on the transport block sizenecessary for the decoding of the interference signal based on theinformation on the modulation scheme and the coding scheme included inthe interference control information and the information on the RBincluded in the DCI of the UE.

Lastly, the exemplary embodiments of the present invention use theC-RNTI (or UE-RNTI) and the common area of the control channel area ofthe UE, thereby minimizing the number of times of the demodulation ofthe interference control information performed by the UE.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for transmitting control information bya first base station (BS) in a wireless communication system, the methodcomprising: receiving from a second BS that is a neighboring BS of thefirst BS, information related to a downlink transmission by the secondBS; generating, based on the received information, control informationused for cancelling an interference caused by the downlink transmissionby the second BS, wherein the control information includes a cellidentifier associated with the second BS, information on a transmissionmode for a second user equipment (UE) served by the second BS, andinformation on precoding used for the downlink transmission by thesecond BS; and transmitting, to a first UE in a cell of the first BS,the generated control information, used for cancelling the interference,including the cell identifier associated with the second BS, theinformation on the transmission mode for the second UE served by thesecond BS, and the information on the precoding used for the downlinktransmission by the second BS, wherein the transmission mode isassociated with a multi antenna transmission corresponding to atransmission scheme of a physical downlink shared channel (PDSCH). 2.The method of claim 1, wherein the generated control information istransmitted to the first UE through one of a common search space (CSS)or a UE specific search space (USS) within a physical downlink controlchannel (PDCCH).
 3. The method of claim 1, wherein the generated controlinformation further comprises at least one of a flag indicating whetherto swap a channel when two transport blocks are transmitted through aspatial multiplexing, an information assigning resource block,information indicating whether a retransmission is performed, amodulation order, a UE identifier associated with the second BS, aninterference control information indicator, or a total number of bits ofcontrol information for cancelling the interference caused by thedownlink transmission by the second BS.
 4. The method of claim 1,wherein, when a load of the first BS is higher than a threshold, thegenerated control information comprises at least one of a flagindicating whether to swap a channel when two transport blocks aretransmitted through a spatial multiplexing, a modulation order, aninterference control formation indicator or a total number of bits ofcontrol information for cancelling the interference caused by thedownlink transmission by the second BS.
 5. The method of claim 1,wherein the generated control information further comprises a modulationand coding scheme (MCS) associated with the second BS.
 6. A base station(BS) in a wireless communication system for transmitting controlinformation, the BS comprising: a BS interface configured to receivefrom a neighbor BS that is a neighboring BS of the BS, informationrelated to a downlink transmission by the neighbor BS; a transmitterconfigured to transmit control information to a first user equipment(UE) in a cell of the BS; and at least one processor configured to:control the BS interface and the transmitter, generate, based on thereceived information, control information used for cancelling aninterference caused by the downlink transmission by the neighbor BS,wherein the control information includes a cell identifier associatedwith the neighbor BS, information on a transmission mode for a second UEserved by the neighbor BS, and information on precoding used for thedownlink transmission by the second BS, and control to transmit, to thefirst UE, the generated control information, used for cancelling theinterference, including the cell identifier associated with the neighborBS, the information on the transmission mode for the second UE served bythe neighbor BS, and the information on the precoding used for thedownlink transmission by the second BS, wherein the transmission mode isassociated with a multi antenna transmission corresponding to atransmission scheme of a physical downlink shared channel (PDSCH). 7.The BS of claim 6, wherein the at least one processor is furtherconfigured to: control to transmit the generated control information tothe first UE through one of a common search space (CSS) or a UE specificsearch space (USS) within a physical downlink control channel (PDCCH).8. The BS of claim 6, wherein the generated control information furthercomprises at least one of a flag indicating whether to swap a channelwhen two transport blocks are transmitted through a spatialmultiplexing, an information assigning resource block, informationindicating whether a retransmission is performed, a modulation order, aUE identifier associated with the neighbor BS, an interference controlinformation indicator, or a total number of bits of control informationfor cancelling the interference caused by the downlink transmission bythe neighbor BS.
 9. The BS of claim 6, wherein, when the at least oneprocessor determines that a load of the BS is higher than a threshold,the generated control information comprises at least one of a flagindicating whether to swap a channel when two transport blocks aretransmitted through a spatial multiplexing, a modulation order, aninterference control formation indicator or a total number of bits forcancelling the interference caused by the downlink transmission by theneighbor BS.
 10. The BS of claim 6, wherein the generated controlinformation further comprises a modulation and coding scheme (MCS)associated with the neighbor BS.